No study of Catholic church music can ignore liturgy. In theory, it provides the basic framework within which music is performed, and it supplies the text with which musicians have to work. In practice the relationship is more complex, and, at the outset, it must be recognised that the study of liturgical theory and theology as an academic discipline did not emerge till the late nineteenth century. This means that much liturgical thinking before that time is implicit rather than explicit in contemporary statements. Moreover, the development of liturgy as an academic discipline signified a change in its character and the sources of authority that underpinned it. This chapter, then, considers five aspects:

the liturgical structure and place of music in the principal services; liturgical books; the nature and function of liturgy; the relationship between liturgy and music; and patterns of liturgical change.